purchase-contract-service.ts

import { Injectable } from '@angular/core';
import { P2pBazaarAnchorModule } from '../p2p-bazaar.anchor.module';
import { Provider } from '../../core/services/tokens';
import { Observable, from, of, zip } from 'rxjs';
import { map, tap, switchMap } from 'rxjs/operators';
import { ethers, Contract, utils } from 'ethers';
import { PurchaseContractModel, ContractState} from '../models';

@Injectable({ providedIn: P2pBazaarAnchorModule })
export class PurchaseContractService {
  
  private readonly abi = [
    'function key() view returns(bytes32 key)',
    'function title() view returns(string title)',
    'function seller() view returns(address sellerAddress)',
    'function buyer() view returns(address buyerAddress)',
    'function price()  view returns(uint weiPrice)',
    'function ipfsHash() view returns(string ipfsHash)',
    'function state() view returns(uint8 state)',
  ];

  constructor(private provider: Provider ) {     
  }

  public loadPurchaseContract(contractAddress: string): Observable<PurchaseContractModel> {
  
    const contract: Contract  = new ethers.Contract(contractAddress, this.abi, this.provider.getSigner());
    return zip(
        contract.key(),
        contract.seller(), 
        contract.buyer(), 
        contract.price(),
        contract.title(),
        contract.ipfsHash(),
        contract.state(),
        )
      .pipe(  
          map(([key, sellerAddress, buyerAddress, weiPrice, title, ipfsHash, state])  => {
          
            const product: PurchaseContractModel = {
              productKey:  utils.parseBytes32String(key as ethers.utils.Arrayish),
              contractAddress,
              sellerAddress : sellerAddress as string,
              buyerAddress: !!buyerAddress ? buyerAddress as string : null,   
              price: utils.formatEther(weiPrice as ethers.utils.BigNumberish),  // $ETH
              title: title as string,
              ipfsHash: ipfsHash as string,
              state: state as ContractState
             };

             return product;
          } )         
        )
    }
}